A pair of stars in our galaxy reveals how light pushes matter around. For the first time, someone directly saw how the pressure of light from stars changes the flow of dust in space.
Such an influx of radiation pressure clears the dust regions around small stars and directs the formation of gas clouds around dying stars (SN: 9/22/20). A sample of dust that sweeps 5,600 light-years around a star in the Cygnus constellation provides a rare laboratory to observe the effect, astronomer Yinuo Han and colleagues report on Oct. 13. nature.
Astronomers have long known that the dust emerging from the star WR 140 and its companion is formed from the gas of the two stars colliding and condensing into dust. But images of the pair taken over the course of 16 years show the dust accelerating away from the stars.
Initially, the star dust departs at about 6.5 million kilometers per hour, the researchers report. This Hercule is enough to make the journey from the Earth to the Moon in a little over half a day. During the cycle of the year, the dust accelerates to about 10 million km/h.
The revelation of the concentric positions of the powder shell was added to the year by year and by bringing the speed. The researchers’ calculations show that the force of accelerating dust is more pressure than the light radiated from the stars, says Han, of the University of Cambridge. “Rational pressure” [becomes apparent] when we put all the pictures next to each other. ”
Not only do those dusty beams feel the impact of light, but they also extend further than any telescopes have ever seen – until this year. Images from the James Webb Space Telescope, or JWST, depict more of the dusty layers around WR 140 and its companion than ever before, Han and another team report Oct. 12. Nature Astronomy.
At first glance, the intricate patterns around the stars look like a giant spider. But the researchers’ analysis reveals that they are enormous, expanding, pyriform dust shells. They are nested within each other, a new one being formed every eight years, as the stars complete another journey around the globe. In the new images, the shells look like cross-sections of rings because we’re looking at them from the side, Han says.
The models do not circle the stars perfectly because the distance between the stars changes as they orbit each other. Since the stars are far away, the density of the colliding gas is too low for the dust to condense — an effect researchers expect.
What is surprising to them is that the gas does not coalesce well when the stars are close to each other. That suggests a “Goldilocks zone” for dust formation: Dust only forms when the separation between the stars is right, creating a series of concentric dust shells from two waves.
“Their Goldilocks zone is a new idea,” says astrophysicist Andy Pollock of the University of Sheffield in England, who was not involved in either study. “A similar thing happens in my field of X-rays.”
In his work, Pollock observed that WR 140 and its partner emit more X-rays as the stars approach each other, but then fewer when they are most closely aligned, showing that there is a Goldilocks zone for X-rays coming from stars. . “It’s interesting to see if there’s a connection” between the two types of Goldilocks zones, he says. “All these are somehow connected.”
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